Free API Tester Online

The API Tester is a free online tool for testing REST APIs by sending GET, POST, PUT, DELETE, and other HTTP requests directly from your browser.

Yes, the API Tester is completely free with no registration required.

Yes, the API Tester lets you configure custom headers, request body (JSON, form data), authentication, and query parameters for each request.

Absolutely. The API Tester processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the API Tester is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the API Tester in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

The API Tester supports a wide range of popular formats and languages. Check the tool interface for the full list of supported options.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The API Tester works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A CORS error happens because the request runs inside your browser, which enforces the same cross-origin rules every web page must follow. If the target API does not return a permissive Access-Control-Allow-Origin header for this site, the browser blocks the response before your code ever sees it, and you get an error instead of a body. This is a security boundary, not a bug in the tester. Public APIs, your own services with CORS enabled, and common developer sandboxes such as JSONPlaceholder, GitHub, and random-user endpoints work without issue. Locked-down internal APIs that omit those headers will keep failing, and the usual fixes are enabling CORS on the server, calling through a CORS proxy, or switching to a desktop client. Try one of the sample endpoints in the tool first to confirm your setup is working.

PUT and PATCH both modify an existing resource, but they differ in scope. PUT replaces the entire resource with the payload you send, so any field you omit is typically wiped or reset to a default; you are expected to send the complete object. PATCH applies a partial update, changing only the fields included in the body and leaving the rest untouched, which makes it ideal for editing a single attribute without resending everything. PUT is also defined as idempotent, meaning repeating the same request leaves the resource in the same state, while PATCH is not guaranteed to be. Choosing the wrong verb is a common cause of unexpected data loss. This tool supports GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS, so you can send each one with a JSON body and compare exactly how the API responds.

HTTP status codes are grouped by their first digit. 2xx means success: 200 OK is a normal response, 201 Created confirms a new resource, and 204 means success with no content returned. 3xx codes signal redirects. 4xx codes are client errors, where something about your request is wrong: 400 bad request, 401 unauthorized (missing or invalid credentials), 403 forbidden (authenticated but not allowed), and 404 not found. 5xx codes are server errors, with 500 internal server error being the most common, meaning the fault is on the API's side, not yours. Knowing the family tells you where to look: fix your request for 4xx, retry or report for 5xx. This tester color-codes the returned status so success, redirects, client errors, and server errors are obvious at a glance the moment your request completes.

Authenticated APIs usually expect a credential attached to each request, and this tester provides presets so you do not have to format them by hand. Choose Bearer Token to send your token as an Authorization header in the standard Bearer scheme, which is the most common pattern for OAuth and JWT-based APIs. Choose API Key when the service issues a key, and place it either in a request header (such as X-API-Key) or as a query parameter appended to the URL, depending on what the docs require. Basic Auth takes a username and password and Base64-encodes them into the Authorization header for you. Because requests run from your own browser and are never proxied through an intermediate server, the tokens and keys you enter stay on your device. Pick the matching preset, paste your credential, and send the request to verify access.

Yes. The Import cURL option parses a pasted curl command and fills in the request for you, reading the URL, HTTP method, headers, request body, and basic authentication so you do not have to rebuild it field by field. This is useful when an API's documentation or a teammate hands you a curl one-liner and you want to run it interactively, tweak a header, or inspect the formatted response instead of squinting at terminal output. It also works in reverse: once a request is set up, the tester can generate a ready-to-paste snippet in JavaScript fetch, Python requests, cURL, PHP, or Go, so you can move from manual testing straight into your codebase. Paste your curl command into the import box, send it, and the response status, timing, and pretty-printed body appear instantly.